A CURRENT EXAMINATION OF DIETARY INTAKES OF FIBER, CALCIUM, IRON, AND ZINC AND THEIR RELATIONSHIP TO BLOOD LEAD LEVELS IN U.S. CHILDREN AGED 1-5 YEARS

A CURRENT EXAMINATION OF DIETARY INTAKES OF FIBER, CALCIUM, IRON, AND ZINC AND THEIR RELATIONSHIP TO BLOOD LEAD LEVELS IN U.S. CHILDREN AGED 1-5 YEARS Stephanie Ann Melchert, M.S. University of Nebraska, 2010 Adviser: Kaye Stanek Krogstrand The effect of lead on the health and well-being of those exposed has been well documented and many efforts have been made to reduce exposure of lead to the United States population. Despite these efforts, many studies have documented cognitive impairments and behavioral problems in children with even low levels of lead in their blood. Previous studies have suggested that a proper diet may have a role in the prevention of elevated blood lead levels in children. The objective of this study was to determine if there was an inverse correlation of blood lead levels (BLL) in children to their dietary intakes of fiber, calcium, iron, and zinc considering low levels of lead exposure. This study examined 1019 children in the National Health and Nutrition Examination Survey (NHANES) conducted from 2005-2006. Data were analyzed using Spearman’s rank correlations to correlate continuous variables to BLL in children and independent samples t-tests were used to compare mean blood lead levels of categorical variables. Results indicate that BLL in children is significantly correlated with and weight, recumbent length/standing height, dietary fiber intake and continine, a marker of cigarette smoke exposure. BLL was not significantly correlated with calcium, iron, zinc, or vitamin C. A significant difference was found in the mean BLL of children who took supplements, lived in smoking homes, as well as those who lived in homes built before 1978. Overall, this study shows that children living in homes built before 1978 remain at greater risk for lead exposure, and adequate dietary fiber intake may provide benefits to children who are exposed to lead.

A Pilot Study of the Relationship of Calcium Intake and Frequency of Injuries In High School Athletes

Little information is available related to adolescent calcium intake and relationships with injuries they might suffer from sport participation. To determine calcium intake of high school athletes, to assess their self reported injury rates, and to examine the relationship between the two over a 12 month period of time. Participants received a questionnaire at their school and completed it anywhere they found convenient. Adolescent athletes in the Lincoln Public School system (n=43) that participated in at least one sport in the past year. Four age groups participated in the study with sixteen year olds having a significantly higher calcium intake at 1297 mg that of fourteen year olds. A variety of sports were represented with largest number of respondents participating in baseball/or softball at (55%). The next most played sport was basketball at (18%). Median total diet calcium was 1144.5 mg with a mean of 1182 mg + 567 mg. For the frequency of injuries that caused a missed practice or game in the past year, ankle injuries were the most common (25%). Knee injuries were the second most common (17%), followed closely by hand injuries (8%). Mean total diet calcium of athletes with five or more injuries that caused a missed practice or game was significantly higher at 1966 mg (P<.05) than athletes mean diet calcium with zero, one, two, and three injuries. Total milk calcium of those who reported three injuries that resulted in broken or fractured bones or dislocated joints was significantly higher (P<.05) at 1286 mg of total milk calcium than those who reported having zero, one, or two breaks or fractures. Athletes with higher calcium intakes have a higher number of reported injuries. This may be the result of increased vigorous activity which leads to increased calorie and calcium consumption. More importantly, this increased activity leads to an increased chance of injury. The greater calcium intake correlated with greater number of injuries may also be because of third parties advising the athletes who get injured to drink more milk and get more calcium in their diets because they have been injuries already.

Improved Regression Estimation of a Multivariate Relationship with Population Data on the Bivariate Relationship

Regression coefficients specify the partial effect of a regressor on the dependent variable. Sometimes the bivariate or limited multivariate relationship of that regressor variable with the dependent variable is known from population-level data. We show here that such population- level data can be used to reduce variance and bias about estimates of those regression coefficients from sample survey data. The method of constrained MLE is used to achieve these improvements. Its statistical properties are first described. The method constrains the weighted sum of all the covariate-specific associations (partial effects) of the regressors on the dependent variable to equal the overall association of one or more regressors, where the latter is known exactly from the population data. We refer to those regressors whose bivariate or limited multivariate relationships with the dependent variable are constrained by population data as being ‘‘directly constrained.’’ Our study investigates the improvements in the estimation of directly constrained variables as well as the improvements in the estimation of other regressor variables that may be correlated with the directly constrained variables, and thus ‘‘indirectly constrained’’ by the population data. The example application is to the marital fertility of black versus white women. The difference between white and black women’s rates of marital fertility, available from population-level data, gives the overall association of race with fertility. We show that the constrained MLE technique both provides a far more powerful statistical test of the partial effect of being black and purges the test of a bias that would otherwise distort the estimated magnitude of this effect. We find only trivial reductions, however, in the standard errors of the parameters for indirectly constrained regressors.